It's not an externality, because it affects the parties involved in the transaction (the car owners), not unrelated third-parties. And since there's no free lun

It's not an externality, because it affects the parties involved in the transaction (the car owners), not unrelated third-parties. And since there's no free lunch - every penny spent on infrastructure by car manufacturers will come from their customers -, you might as well unbundle the two, and let other companies compete for that.